package club.xiaojiawei.hash;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author 肖嘉威
 * @version 1.0
 * @date 4/30/22 3:11 PM
 * @question 18.四数之和
 * @description 给你一个由 n 个整数组成的数组 nums ，和一个目标值 target 。请你找出并返回满足下述全部条件且不重复的四元组 [nums[a], nums[b], nums[c], nums[d]] （若两个四元组元素一一对应，则认为两个四元组重复）：
 * 0 <= a, b, c, d < n
 * a、b、c 和 d 互不相同
 * nums[a] + nums[b] + nums[c] + nums[d] == target
 * 你可以按 任意顺序 返回答案 。
 */
public class FourSum18 {

    public static void main(String[] args) {
        int[] nums = {1,-2,-5,-4,-3,3,3,5};
        List<List<Integer>> result = fourSum(nums, -11);
        System.out.println(result);
//        -2, -2, -2, -1, 0, 0, 1, 2, 3, 4
//        [-2, -2, 0, 4],[-2, -2, 1, 3],[-2, -1, 0, 3],[-2, 0 ,0 , 2],[-1, 0, 0 ,1]
    }

    /**
     * 排序+双指针（同三数之和 ThreeSum15）
     * @param nums
     * @param target
     * @return
     */
    public static List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        ArrayList<List<Integer>> result = new ArrayList<>();
        int length = nums.length;
        if (length < 4){
            return result;
        }
        for (int f = 0; f < length - 3; f++) {
            if (f != 0 && nums[f] == nums[f - 1]){
                continue;
            }
            for (int t = f + 1; t < length - 2; t++) {
                if (t != f + 1 && nums[t] == nums[t - 1]){
                    continue;
                }
                long num = (long) target - (long) nums[i] - (long) nums[j];
                if (num >= 0 && num < nums[t + 1]){
                    break;
                }
                int l = t + 1, r = length - 1, temp;
                while (l < r){
                    if ((temp = nums[l] + nums[r]) > num){
                        r--;
                    }else if (temp < num){
                        l++;
                    }else {
                        ArrayList<Integer> list = new ArrayList<>();
                        list.add(nums[f]);
                        list.add(nums[t]);
                        list.add(nums[l]);
                        list.add(nums[r]);
                        result.add(list);
                        l++;
                        r--;
                        while (l < r && nums[l] == nums[l - 1]){
                            l++;
                        }
                        while (l < r && nums[r] == nums[r + 1]){
                            r--;
                        }
                    }
                }
            }
        }
        return result;
    }

    /**
     * 官方-排序+双指针+剪枝（同三数之和 ThreeSum15）
     * @param nums
     * @param target
     * @return
     */
    public List<List<Integer>> fourSum2(int[] nums, int target) {
        List<List<Integer>> quadruplets = new ArrayList<List<Integer>>();
        if (nums == null || nums.length < 4) {
            return quadruplets;
        }
        Arrays.sort(nums);
        int length = nums.length;
        for (int i = 0; i < length - 3; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            if ((long) nums[i] + nums[i + 1] + nums[i + 2] + nums[i + 3] > target) {
                break;
            }
            if ((long) nums[i] + nums[length - 3] + nums[length - 2] + nums[length - 1] < target) {
                continue;
            }
            for (int j = i + 1; j < length - 2; j++) {
                if (j > i + 1 && nums[j] == nums[j - 1]) {
                    continue;
                }
                if ((long) nums[i] + nums[j] + nums[j + 1] + nums[j + 2] > target) {
                    break;
                }
                if ((long) nums[i] + nums[j] + nums[length - 2] + nums[length - 1] < target) {
                    continue;
                }
                int left = j + 1, right = length - 1;
                while (left < right) {
                    int sum = nums[i] + nums[j] + nums[left] + nums[right];
                    if (sum == target) {
                        quadruplets.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
                        while (left < right && nums[left] == nums[left + 1]) {
                            left++;
                        }
                        left++;
                        while (left < right && nums[right] == nums[right - 1]) {
                            right--;
                        }
                        right--;
                    } else if (sum < target) {
                        left++;
                    } else {
                        right--;
                    }
                }
            }
        }
        return quadruplets;
    }
}
